Figure of merit (FOM) is defined as the product of the on-resistance Ron of a device and the parasitic capacitance Coff of the device, i.e., FOM=Ron×Coff. FOM measures the performance of a switching device or technique and is independent of the critical dimension of the device. In addition, the smaller the FOM, the higher the performance of the device.
Parasitic junction capacitance of a SOI device is related to the thickness of a top silicon layer of the SOI wafer from which the device is fabricated. Therefore, there is a need for a method for efficient and easy local thinning of a top silicon layer of a SOI wafer in order to form a SOI wafer structure with a locally thinned top silicon layer.